Error: ‘ptrdiff_t’ does not name a type

I have tried to install qt-x11-free-3.3.6 on the new Ubuntu OS (12.04 LTS) (gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3).
The configuration went well but when I tried to run "make" I got the following error message:
....
....
../include/qvaluelist.h:88:13: error: ‘ptrdiff_t’ does not name a type
../include/qvaluelist.h:164:13: error: ‘ptrdiff_t’ does not name a type
....
....

../include/qmap.h:107:13: error: ‘ptrdiff_t’ does not name a type
../include/qmap.h:223:13: error: ‘ptrdiff_t’ does not name a type
.....

It's a common error with relative new libc and... Just add
@#include <stddef.h>@
to files on which does the compiler complains. You may have also troubles with png plugin if you have selected --system-libpng and you have 1,5* libpng... where is an patch on the web... for example "here":http://www.linuxfromscratch.org/patches/downloads/qt/